/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 4 -*- */
/* vi: set expandtab shiftwidth=4 tabstop=4: */

#include <stdint.h>

#ifndef WORDS_BIGENDIAN
#define get16bits(d) (*((const uint16_t *) (d)))
#else
#define get16bits(d) ((((const uint8_t *)(d))[1] << UINT32_C(8))    \
                      +((const uint8_t *)(d))[0])
#endif

/** \brief  hash by Paul Hsieh
 *
 * Copyright Paul Hsieh (C) 2004, 2005
 * License: http://www.azillionmonkeys.com/qed/weblicense.html
 */
class PaulHsiehHash32 {
 public:

    const char* name() const
    {
        return "PaulHsieh";
    }

    /** \brief algorithm optimized for uint32
     */
    uint32_t hash32(uint32_t x) const
    {
        uint32_t hash = x >> 16;
        uint32_t tmp    = ((x & 0x0000ffff) << 11) ^ hash;
        hash = (hash << 16) ^ tmp;
        hash += hash >> 11;
        hash ^= hash << 3;
        hash += hash >> 5;
        hash ^= hash << 2;
        hash += hash >> 15;
        hash ^= hash << 10;
        return hash;
    }

    uint32_t hashStr(const char* data, int len) const
    {
        uint32_t hash = 0, tmp;
        int rem;

        if (len <= 0 || data == NULL) return 0;

        rem = len & 3;
        len >>= 2;

        /* Main loop */
        for (;len > 0; len--) {
            hash  += get16bits (data);
            tmp    = (get16bits (data+2) << 11) ^ hash;
            hash   = (hash << 16) ^ tmp;
            data  += 2*sizeof (uint16_t);
            hash  += hash >> 11;
        }

        /* Handle end cases */
        switch (rem) {
        case 3: hash += get16bits (data);
            hash ^= hash << 16;
            hash ^= data[sizeof (uint16_t)] << 18;
            hash += hash >> 11;
            break;
        case 2: hash += get16bits (data);
            hash ^= hash << 11;
            hash += hash >> 17;
            break;
        case 1: hash += *data;
            hash ^= hash << 10;
            hash += hash >> 1;
        }

        /* Force "avalanching" of final 127 bits */
        hash ^= hash << 3;
        hash += hash >> 5;
        hash ^= hash << 2;
        hash += hash >> 15;
        hash ^= hash << 10;

        return hash;
    }
};
